Field of the Invention
The invention relates to a device and the method for administering and assigning radio transmission channels within a radio zone in a mobile radio network.
Third generation mobile radio networks will make it possible for a mobile subscriber to access a large number of communications services with different transmission properties and transmission demands. In order to implement these possibilities, the limited number of radio transmission channels on the air interface must be administered and assigned in an optimum way without experiencing restrictions as a result of the different requirements which are placed on the transmission of the communications services.
Two methods for dynamically administering and assigning radio transmission channels (DCA--Dynamic Channel Allocation) are known from the article "Channel Assignment Schemes for Cellular Mobile Telecommunications Systems: A Comprehensive Survey"; IEEE Personal Communications; Jun. 1996; pages 10-31 by I. Katzela, M. Naghshineh. In both methods, all the radio transmission channels are combined in a central pool and assigned dynamically to the radio cells when new communications links occur. Here, each radio transmission channel can be used in each radio cell provided that the interference conditions are met.
A distinction is made between a centralized and a distributed DCA method. In the case of the centralized DCA method, a central controller assigns a radio transmission channel temporary for a communications link, whereas in the case of the distributed DCA method the base station, at which the connection request occurs, assigns a radio transmission channel temporary for a communications link. In the base station, the assignment is carried out here solely on the basis of the base station's own information concerning the interference situation and the capacity utilization.
These two methods for administering and assigning the radio transmission channels have the disadvantage that only the transmission criteria are used as the basis for the assignment decisions and the respective requirements placed on the transmission by the different communications links are not taken into account.
U.S. Pat. No. 4,144,412 discloses a method for assigning radio channels to a calling mobile station in a mobile radio network, in which a mobile base station which is suitable for setting up the radio link and a free voice channel are selected in a central radio control device. This selection is made on the basis of intensity measurements of the signals transmitted by the mobile station through the use of mobile base stations which are connected to the radio control device. The respective intensity measurements are compared in a radio control device, and the mobile base station with the maximum intensity is selected. A free voice channel of the selected mobile base station is subsequently determined and assigned to the radio link. The mobile base stations and the voice channels or their current status are administered in memory devices in the radio control device.
Published European patent application EP 0 504 122 A2 discloses a method for a handover control in a cellular communications system. In this method, not only the base station which is currently in charge of supplying radio sevices but also a respective adjacent base station can also initiate a handover of a mobile station.
International patent publication WO 95/34957 discloses a method for the adaptive and automatic planning of the assignment of frequencies to transmission channels within a number of radio cells in a cellular communications system. In this context, quality parameters are determined for all the available frequencies. A respective frequency is assigned to each transmission channel according to an analysis of the measured quality parameters in conjunction with predefined criteria.
The article "Implementation and Performance Analysis of Multi-Algorithm Dynamic Channel Allocation in a Wideband Cellular Network" by J. Vucetic, 1996 IEEE International Conference on Communications (ICC), Converging Technologies for Tomorrow's Applications, Dallas, Jun. 23-27, 1996, Vol. 3, Jun. 23, 1996, pages 1270-1274 discloses a method in which the probability of blocking in a digital cellular network is reduced by using a plurality of dynamic channel assignment algorithms. For this purpose, a plurality of algorithms are implemented simultaneously in one switching device of the network. A respectively suitable algorithm which ensures a minimum probability of blocking is selected as a function of a current traffic load and an interference situation.